Nissan’s senior vice-president of research and development for the Americas, Carla Bailo, sent an open letter to US Leaf owners after the company performed tests on seven cars from Phoenix, Arizona, after owners flagged concerns with loss of battery life. Summer temperatures in Phoenix regularly soar above 40 degrees.

The company has always maintained battery life loss is expected over time, saying it expects the Leaf battery to retain 80 per cent of battery capacity after the first five years of ownership. At that rate, the Leaf’s official range of 160km will be cut to 128km.

However, Bailo concedes the 450 Leaf owners in the state of Arizona can expect 76 per cent (121.5km) after five years “or a few percentage points lower than the global estimate”.

“Some vehicles in Arizona will be above this average, and some below,” she says. “Factors that may account for this differential include extreme heat, high speed, high annual mileage and charging method and frequency of the Nissan Leafs in the Phoenix market.”

Australian coastal cities don’t achieve the same sustained high temperatures as in Arizona; however, a post on the mynissanleaf.com forum indicates that abnormally high losses in battery life may also occur in more temperate climates.

Leaf owner “Garygid” from Laguna Hills in southern California, says after driving fewer than 15,000 kilometres in 18 months in his Leaf, his car has already lost 10 per cent of its battery capacity – nothing in the first six months, 2 per cent in the second six months and 8 per cent in the third six months.

“If I continue to lose another 8 per cent by the end of the second year, that will be 18 per cent in two years. I will have to wait to see what happens,” he posted.

“However, losing 16 per cent per year is not what Nissan lead me to believe that the Leaf would deliver. I will know more in six months.”

Southern California’s climate is considered comparable to the east coast of Australia, with similar summer average temperatures and weather extremes.

Another forum user, Ron from San Francisco, posted he had experienced a 10 per cent loss “in actual measured range” in 15 months, during which time he had travelled 16,000 kilometres.

“This is faster loss than I expected in my climate. For now, it isn't impacting me ... but I hope the loss does slow down, because I may be unable to comfortably complete common trips I do if the loss doubles in another year.”

In her open letter, Bailo says rapid early losses in battery capacity are unlikely to continue. “While your Leaf may have been able to travel a certain distance or more on a charge when new, its range will decrease as the battery ages, miles accumulate and gradual capacity loss occurs. This loss in capacity will occur most rapidly in the early part of your battery’s life, but the rate should decrease over time,” she says.

The Leaf utilises “air cooling” to counter high operating temperatures, unlike other EVs from General Motors, Tesla and Ford that use more sophisticated active thermal management systems that circulate cool liquid around the batteries.

A group of Arizona-based Leaf owners recently performed their own test, organising a highway-based driving route and recording the distance travelled by each of the 12 participating cars.

The longest distance was 127.4 kilometres by a 2012 model that had travelled 4000km, while a 2011 model that had 46,500km on the clock covered just 94.9km.

The test, organised by US-based Leaf owner Tony Williams, concluded that a Nissan assertion that the cars’ instruments were not always indicative of actual charge was correct.

However, Williams also says a statement from Nissan global executive vice-president Andy Palmer that there is “no problem” with the Leaf battery was “sheer stupidity”.

“Nissan really needed to get the Leaf right the first time, and they did an absolutely incredible job overall. I tell everybody know that it’s a fantastic car with one fatal flaw,” Williams says.

Nissan Australia, which guarantees the Leaf’s battery pack for eight years of life or 160,000 kilometres, is seeking more information and was unable to comment.

Nissan Australia has sold just 57 examples of the $51,500 electric car since it went on sale in June.